Vaporizer



Sept 26, 195

B. H. JENNING$ AL VAPORIZER Filed May 10, 1946 HEATING ELEMENTLLNIZUEIFL Wmmk Gun 70 60 50 4O 2o TRIETHYLENE GLYCOL Z0 30 9g WATER PERC Patented Sept. 26, 1950 VAPOEIZER Burgess H. Jennings and Edward Bigg,Evanston,

and Franklyn C. W. Olson, Wilmette, 111., assigners, by mesneassignments, to Research Corporation, New York, N. Y., a corporation ofNew York Application May 10, 1946, Serial No. 668,946

4 Claims. 1

This invention relates to an apparatus for vaporizing liquid and moreparticularly to an apparatus for producing a substantially constantproportion of constituent vapors from a miscible mixture of two or moreliquids having different boiling points.

Controlled vapor output from a vaporizer becomes important when theamount and concentration of a vapor being delivered to an enclosed spacedetermines the intended effectiveness of the vapor. Thus, if a vapor isused to sterilize an atmosphere and the vapor concentration is animportant factor in achieving the desired sterilization, correctvaporizer design to give the desired vapor concentration is required. Asan example, of such a requirement, it has been found that a compositevapor consisting 01' 3% triethylene glycol vapor and 97% Water vapor iseffective in achieving air sterilization and to prevent air-borneinfection when supplied to a treated space in adequate quantity.

Assume that such a vapor proportion can be obtained by boiling amiscible binary-mixture of 90% triethylene glycol and water. An ordinaryvaporizer would be ineffective to maintain'the desired 3% triethyleneglycol vapor-97% water vapor output because, as the binary liquidmixture of triethylene glycol and water is boiled, more water thantriethylene glycol is vaporized with the result that the concentrationof the liquid in the vaporizer would change and, hence, the vapor ratiooutput would also change. Also, because the miscible binary mixturewould now contain a greater relative proportion of triethylene glycol towater than did the original mixture, the boiling point, and hence thetemperature of the mixture, would increase; Continued increase inmixture temperature as the concentration of triethylene glycolincreases, could result in overheating the mixture and the possiblerelease of impurities through break down of the triethyleneglycol. Suchimpurities could be detrimental to air sterilization and to individualsbreathing such air. Thus, when the generated vapor is used for airsterilization and germicidal purposes it is important to prevent theintroduction of impurities, which might raise the possibility oftoxicity, into air being breathed by persons. If a source of suchimpurities could be overheating of the liquid in a vaporizer, broughtabout by an incorrect concentration of such liquid where theconcentration is dependent upon the relative proportion of componentsforming the liquid, then a vaporizer is needed that will maintain liquidconcentration, and hence the vapor concentration, substantiallyconstant. We have found that .a 3% triethylene glycol vapor-9'7 watervapor output ratio, when maintained substantially constant, can bedelivered to a treated space without fear of a chemical breakdown of theliquid mixture undergoing heating;

While we have used triethylene glycol and water as an example, theproblem of maintaining liquid concentration substantially constantexists Whenever one heats a miscible mixture 01' liquids havingdifferent boiling points and it is desired to maintain a vapor output ofsubstantially constant predetermined concentration, The liquidconcentration required to maintain the correct output vapor ratio can bedetermined from the temperature composition diagram of the particularmiscible mixture being used. A satisfactory vaporizer for such a mixturewill include means to compensate for. the greater loss of the morevolatile liquid component if the original liquid concentration is to bemaintained and, hence, the output vapor ratio or concentration is toremain substantially constant.

Accordingly, the principal object of the present invention is to provide.an apparatus for introducing a vapor of substantiallyconstant'predetermined component proportion into an atmosphere and tomaintain the output vapor propore tion substantially constant duringoperation of tional liquid to the liquid mixture during heattween thethermal element and the means to the apparatus. Other objects of thepresent invention are to provide apparatus for vaporizing liquid toproduce vapor of substantially constant component proportions whichincludes means to maintain the liquid concentration substantiallyconstant during heating; to provide such an apparatus which includesmeans to admit addiing of the latter and to control the rate ofadmission of the additional liquid; and to providev such an apparatuswhich includes a thermal element and a positive mechanical connectionbetric heating coil.

"low metal sheet members 23.

lar 29,. as is shown in Fig. 1.

3 the remaining elements are shown in their respective front elevationalviews;

Fig. 2 shows a temperature composition diagram for a miscible binarymixture of triethylene glycol and water.

Referring to Fig. 1, the principal elements of the vaporizer are a tankIt] for containing the liquid II to be vaporized, a heating element [2for heating said liquid, and a bellows member I3 mechanically coupled toa valve assembly 14 to control the admission of a liquid component totank Ill to thereby control the concentration .of the liquid mixture inthe tank.

Tank ill can be either a circular or squared metal container, the sizebeing dependent upon the quantity of liquid to be vaporized. In theembodiment shown in Fig. 1, tank In is mounted on support members 15 ofsufficient height to raise the bottom of the tank above the floor levelto permit the heating element 12 to be positioned beneath the bottom ofthe tank. Heating element I2 is attached to the underside of tank l6 bya suitable means, not shown. Heating element I2 can be either a flamesource of heat or a convective or radiant heater, such as an elec- Inour embodiment we use an electric radiant heating element which can beeither of 1000 watts or 2000 watts rating or other appropriate value,depending upon the power source available, the size of th tank beingheated, and the desired rate of vaporization. V I

It isobvious, though not shown, that by means of either a voltage orresistance control, the heat output of a particular radiant heater couldbe controlled as desired to varythe rate of vaporization.

Tank 16 is flared at I6 to receive a cover 11, attached to the tank bymeans, such as flange bolts- 18-. Attached to cover I1, and held' bymeans such as nuts I9, are a pair of metal support rods 26 which arethreaded at their lower ends 2|. Threaded ends 21 extend throughopenings in a support block 22, the latter being made of substantiallynoncorrosive material. Intermediate the support block 22 and theunderside of cover- 11, support rods are enclosed by hol- Nuts 24 engagethreaded ends 21 of support rods 20 and hold support block 22 inabutting engagement with the lower ends of sheath members 23, as shownin Fig. 1.

- Support block 22, in turn, supports a metallic bellows member 13 bythe attachment thereto of athreaded support rod 25 which is in threadedengagement with block 22,. If desired, bellows member l3 could b upp edby m m ers extending from the sides of the tank In, or even by members,preferably insulated, extending from thebottom of said tank. Bellowsmember 13 has an actuating rod 26 attached thereto and extendingfrom thetop'thereof. As is shown in Fig. 1, rod 26 extends through the cover 11,

pipe 28 has an outer flange 3| integral therewith d pi ring 36, enga es.he pper s riaee of flan e 3 5, thereby holdin pe 2 aga n t Pipe 28 canbe released by loosening ring 36. Pipe 28 is threaded at it upper endinto the lower portion of valve block 14.

Valve block I4 contains a chamber 32. Cham ber 32 is connected throughpassage 33, to liquid inlet 34. The bottom portions of chamber 32 slope,as shown, to provide a valve seat 35, which is engaged by the valve seatengaging portion 36 of valve head 21. Valve head 21 is biased to seatedposition by spring 33 or, if spring 39 is omitted, by the action ofgravity. Passage 3?, of greater diameter than rod 26, connects chamber32 to outlet pipe 28. Outlet pipe 28 is connected, as shown, to permitentry of liquid into tank I6. Valve block 14 is suitably supported bysupport means, not shown, to maintain the necessary alignment to permitthe desired valve action.

Vapors generated by heating tank Ii) leave the tank through outlet 38.Although in the particular embodiment shown, a single outlet through thecover I! is shown, it is obvious that a plurality of such outlets couldbe provided in the cover, or near the top of the vertical sides of tank10. Cover H can be raised .from tank ill by removing threaded cap member40 on valve block 13 and then removing valve head 21, or rod 26 can beremoved in its entirety, and then loosening nuts 18 and 19. If rod-26 isnot re.- moved, the cover can be raised vertically or, if rod 26 isremoved, the covercould be tilted. In either event, the cover can beraised sulliciently to permit inspection of the interior of th tank 10and to admit liquid into tank ll] from the top if it is desired to addthe liquid in this manner. An additional liquid inlet pipe 4!, having aflow control valve 32, is shown connected to tank 10 at 43. The initialliquid mixture preferably can be added through this connection. Also,this liquid entry, which is manually controllable, per. mits addition ofa single component ofthe mixture if such is desired. Drain-cock M isprovided to permit drainage of the tank.

Since we utilize an electric radiant heating element, we show in Fig. 1,lead-in wires 45 from an electrical power source, either or 220 volts,dependent upon the size and rating of the particular heater being used.Switch 46 provides manual on or off connection of the heater element tothe power source. A suitable cutout, such as electromagneticcut-out' ll,is also pro.- vided. Cut-out 41 is controlled and connected by leads 48to an adjustable thermostat 49 which In Fig. 1, we show tank 10 andcover 11 insulated with an insulation covering 56, which is provided toreduce heat loss from the tank. An air-cell type asbestos, 1% thick, issuitable. When the liquid mixture contained in tank It] is corrosive innature, or produces corrosive vapors, it is necessary to line metalsurfaces which are exposed to the vapors, such as the interior of thetank nd the underside of the cover member, with a suitable corrosionresistant material. Thus we show,,at 5|, an inner lining of copperplating to prevent tank corrosion where a miscible binary mixture oftri-ethylene glycol and Water is the solution to be vaporized in ourapparatus.

The operation of our apparatus is as follows:

.tank it could be filled from inlet pipe iii. lows member l3 may also befilled with a miscible The liquid concentration of a miscible mixturenecessary to obtain a substantially constant predetermined proportionbetween the constituent vapors generated upon heating said mixture canbe determined from the temperature composition diagram of the particularmixture chosen. Thus, we show in Fig. 2, as an example, the temperaturecomposition diagram of a miscible binary mixture of triethylene glycoland water.

Assume that we desire a vapor proportion of 3% triethylene glycol vaporto 97% water vapor. This proportion is indicated at point A on thediagram shown in Fig. 2. A vertical line from point A intersects thevapor composition curve at point B. A horizontal lin drawn from point Bintersects the liquid composition curve at point C. A vertical linedropped from point C intersects the horizontal axis at point D. Thereading at point D shows 90% triethylene glycol and water as thecomposition of the liquid to be added to tank I0.

Fig. 2 further shows that this liquid boils at 260 F. to produce vaporshaving a proportion of 3% triethylene glycol vapor and 97% water vapor.

Tank It] is filled to the desired level, at least to a level sufiicientto immerse the bellows member 13 with a miscible mixture of liquidshaving different boiling points which, as we have indi cated as anexample, can be a miscible binary mixture of triethylene glycol andwater. The filling of tank it can be accomplished by raising cover I? topermit entry of the liquid, or better,

Bel-

mixture having the same liquid composition as the liquid initially putinto tank id, or with a different liquid having the same boilingtemperature as the liquid initially put into the tank. Bellows member l3should then-be hermetically sealed. Before heating is commenced, thecover is tightened and all connections checked.

Heater element I2 is then energized. When the liquid in tank It boils,and still taking as an example a miscible binary mixture of triethyleneglycol solution, having 90% triethylene glycol and 10% water, more waterthan triethylene glycol is vaporized. Vaporization of more water thantriethylene glycol raises the concentration of the latter in the mixtureremaining in tank i6 and, consequently, raises the boiling pointthereof. This can be observed from the liquid composition curve shown inthe diagram in Fig. 2.

Since bellows member 13 contains a liquid having the same boiling pointas the liquid initially admitted to tank 10, when the composition of thelatter is changed and consequently its boiling point is changed, whichchange is assumed to be a rise in boiling point, the liquid in thebellows will vaporize. Vaporization of this liquid causes the bellows toexpand and, through rod 26 the bellows unseats valve head 27. When valvehead 2? is unseated liquid flows from chamber 32 through passage 31 andpipe 28 into tank ill. Still continuing the example of triethyleneglycol and water, the liquid admitted through the valve arrangement canbe either water or a miscible binary mixture of triethylene glycol andwater in which the proportion of triethylene glycol to water issubstantially the same, or less, as the proportion of triethylene glycolvapor to water vapor in the vapor output. If the liquid added is amixture of triethylene glycol and water having these components insubstantially the same, as defined hereafter, proportion as theconstituent vapors in the output, both theglycol and the water, alreadyin the tank, are replenished whereas, if the liquid added is simplywater, or a mixture of triethylene glycol and water having thesecomponents in less proportion than the constituent vapors in the output,there is a slow loss of triethylene glycol and a resultant slow drop inthe level of the liquid in the tank. However, as this liquid level dropwould only be appreciable after prolonged heating it does not interferewith practical operation of our apparatus and when required, additionalpure triethylene glycol can be admitted through inlet pipe 4i. When adilute mixture of triethylene and glycol is added to the relativelyconcentrated mixture being heated in the tank to replenish theconcentrated mixture, it is necessary to provide a slightly higherproportion of triethylene glycol in the liquid being added than theproportion to triethylene glycol vapor in the vapor output. Thus, if thetriethylene glycol vapor in the vapor output is 3% of the total vapor,the proportion of triethylene glycol liquid in the liquid being added toreplenish the original mixture should be approximately 5%. This slightlyhigher value is required because replenishing cannot take placeinstantaneously and it is necessary to compensate for the loss of volumedue to a slight time lag in the operation of bellows member I3; However,the 5% value is substantially the'same as the 3% value in the outputvapor. In either event, whether water alone is added to the originalmixture or a mixture of water and triethylene glycol of substantiallythe same or less proportion as the vapor proportion, the net result isto lower the triethylene concentration in the mixture being heated and,hence, the boiling point of that mixture is lowered. That lowering thecor'icentrationv of triethylene glycol lowers the boiling point can beobserved from Fig. 2. This lower temperature causes bellows member I3 tocontract, and through rod 26, to reseat valve head 2?! to shut off theflow through passage 31 and pipe 28, thereby stopping the entry of waterinto tank Ii]. On continued heating this cycle is repeated. Thesensitivity of the control effected by bellows member i3 can becontrolled by choice of the type of bellows used.

It is necessary to have a low pressure liquid source, using either wateror dilute mixture of triethylene glycol and water as an example,connected to inlet 34 to allow the liquid entering tank It through valvearrangement M to mix adequately with the liquid already in the tank.This liquid flow should be restricted to two gallons per minute, orless, otherwise the admitted liquid will mix inadequately and may formcold pockets which, upon heating, may erupt and possibly force hotglycol directly through opening 38. Although we have not shown a highlevel liquid safety cut-01f to stop the flow of liquid into the tank inthe event of a bellows failure, it is obvious that such an arrangementcould be provided.

It will be seen that we have provided an apparatus for-introducing avapor into an atmosphere where the vapor is of substantially constantcomponent proportion and where this component proportion is maintainedby controlling the concentration of the liquid which is heated toproduce the vapor. Although we have used the illustration of a binarymixture, the teach ing of our invention can be applied to misciblemixture of more than two liquids having different boiling points whereit is desired to main.-

tain the vapor output ratio substantially constant by maintaining the.liquid concentration, and the apparatus. we. have described can,withinvention, be. readily adapted for such use.

Thus, while we have described a particular embodiment of our invention.it is to be understood that we do not wish. to be restricted to this,and that we intend to. cover all modifications thereof which wouldbe,apparent to one skilled in the art and which come within the spirit andscope of our invention.

Weclaim:

1. In apparatus for generating and delivering to the atmosphere atpredetermined proportion of glycol and water vapor, the combination of acontainer open to the atmosphere and adapted to contain a mixture ofglycol and water in specified proportions, means for heating saidmixture to cause vaporization to occur, means for replenishing waterdissipated by vaporization, said replenishing means including an inlet,and control means for regulating the admission of the replenishingliquid through said inlet to the container, said control means includinga variable flow valve and a. thermostatic bellows, said bellows beingconnected at one end to said valve for controlling its position andhence the rate at which replenishing liquid is admitted to thecontainer, said bellows containing a liquid which boils at a temperaturecorresponding substan specified proportions, means iorheating saidmixture, means. for replenishing, in substantially the same. proportionas glycol and water are lost out departing from the spirit and scopev ofour through vaporization, the liquid dissipated by vaporization,v said.replenishing means including an inlet, and control means for regulatingthe admission of the replenishing liquid through said inlet to thecontainer, said control means including a variable flow valve and athermostatic bellows, said bellows being connected at one end to saidvalve for controlling its position and hence the rate at whichreplenishing liquid is admitted to the container, said bellowscontaining a liquid which boils at a temperature correspondingsubstantially to that of said liquid mixture of specified proportions,whereby any tendency for the glycol concentration of the liquid mixturein the container to increase will result in the admittance of additionalwater and glycol to oiiset that tendency.

3. The apparatus as set forth in claim 1 in which a thermostatresponsive to the temperature of the glycol mixture in the containerautomatically controls the operation of said heating means.

l. The apparatus as set forth in claim 1 in which the variable flowvalve is spring-pressed to closed position.

BURGESS H. JENNINGS. EDWARD BIGG. FRANKLYN C. W. OLSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,290,425 Guernsey July 26, 19422,369,900 Jennings et a1. Feb. 20, 1945

